1. Field of the Invention
The present invention relates to a method and an apparatus for measuring a wire-shaped object, more particularly, to a method and an apparatus for measuring a three-dimensional configuration of a bonding wire for a semiconductor device in a short time, by using a light beam projection method. Note, this bonding wire is, for example, for an electrical connection between a semiconductor chip and a lead frame, or an IC chip and a package, and the present invention is applied to detect an abnormal approach portion and an abnormal connection portion between two adjacent bonding wires or a bonding wire and a semiconductor chip (substrate), by measuring the three-dimensional configuration thereof.
2. Description of the Related Art
Recently, the number of bonding wires connected between a semiconductor chip (IC chip) and a lead frame (package) has multiplied, in accordance with a high densification and miniaturization of the semiconductor chip; for example, it is not unusual for one semiconductor chip to include more than one hundred bonding wires.
In such a semiconductor chip including over one hundred bonding wires, the wire pitch (space between adjacent bonding wires) is very narrow, e.g., about 0.2 mm, and thus production errors may frequently occur due to a short-circuiting between adjacent bonding wires or a bonding wire and a semiconductor chip, during a wire-bonding process and the like.
In the prior art, the test for detecting the production errors is carried out by a manual visual observation using a microscope, and thus the accuracy and speed of the test are limited. Further, in the prior art, the shape of the bonding wire is only measured two-dimensionally, in a horizontal plane, and thus a defective portion of an extreme approach, or a short-circuiting between the wire and a semiconductor chip located under the wire, cannot be detected in a vertical plane.
In consideration of the above, many methods and apparatuses for measuring the three-dimensional configuration of a wire-shaped object (bonding wire) have been disclosed.
In the prior art, three methods are used to measure the three-dimensional configuration of a bonding wire, i.e., a floodlight method, a stereoscopic vision method, and a variable focus method. Concretely, in the prior art, apparatuses for measuring a three-dimensional configuration of a wire-shaped object (for example, a bonding wire) are disclosed in Unexamined Japanese Patent Publication (Kokai) Nos. 63-6679, 1-116405, and 1-246841; however, these apparatuses require long time for measuring the three-dimensional configuration of the bonding wire, and further, some of these apparatuses cannot correctly measure the three-dimensional configuration of the bonding wire.